Dermatology and Dermatopathology

Summary

Dermatologists diagnose and treat medical conditions of the skin, including acne, rosacea, psoriasis, warts, hair loss, and various forms of skin cancer. Dermatopathologists analyze the mechanisms of skin diseases and perform microscopic diagnoses based on the tissue samples submitted by dermatologists. Skin disorders have a high prevalence and can affect patients of all ages, from neonates to older adults. Because of the great variety and dynamic nature of the lesions, specialties focusing on the skin are among the most complex in medicine.

Definition and Basic Principles

Dermatology is the branch of medicine dedicated to diagnosing, treating, and preventing diseases and conditions of the skin, hair, nails, and mucous membranes. A subspecialty of pathology and dermatology, dermatopathology focuses on studying the mechanisms of skin diseases and on the microscopic examination of cutaneous tissue.

Dermatologists assess the appearance and distribution of any abnormalities in the skin, identifying primary and secondary lesions. These lesions can manifest in numerous forms, including macules, papules, plaques, nodules, pustules, cysts, wheals (hives), scales, fissures, and scars. The patient may complain of itchiness (pruritus), pain, or hair loss or may be uncomfortable with the appearance of a skin area. If a diagnosis is not readily apparent, the dermatologist performs a skin biopsy. A dermatopathologist examines the tissue under a microscope and renders a pathological diagnosis.

The skin is the largest and most visible organ of the human body, with essential functions in storage, absorption, thermoregulation, vitamin D synthesis, and protection against pathogens. It is readily accessible to the examiner. However, the potential abnormalities are numerous, and the differential diagnoses are extensive, rendering dermatology one of the most complex medical disciplines. Although the field has been morphologically oriented for centuries, advances in molecular medicine and genetics have opened new opportunities for understanding the pathogenesis of skin diseases and for improved diagnosis strategies. An evolving interrelationship with other disciplines, such as plastic surgery and endocrinology, has been expanding the frontiers of this medical specialty.

Background and History

People have been concerned with the health and appearance of their skin throughout history. Egyptian physicians used arsenic applications to treat skin cancer and sandpaper to smooth scars. Queen Cleopatra was known for her cosmetic knowledge. Geoffrey Chaucer's The Canterbury Tales (1387–1400) and William Shakespeare's plays contain numerous references to unsightly skin afflictions, such as boils, carbuncles, and scabs. Not surprisingly, their appearance is frequently a metaphor for character flaws.

Some of the first skin treatments were undoubtedly borrowed from the plant world, making use of leaves, flowers, and roots. The juice of the aloe vera plant, for example, is an ancient and effective remedy that continues to be used for some skin conditions. For centuries, physicians treated a wide range of afflictions, from rashes to wounds, using oils, powders, and salves they mixed themselves. Sunlight was used by European physicians in the eighteenth and nineteenth centuries to treat psoriasis and eczema.

Starting in the nineteenth century, a true revolution in biology galvanized the progress of skin sciences. The terms “dermatology” and “dermatosis” were introduced. In the late 1800s, dermatologists began using a variety of chemicals to smooth facial wrinkles and scars. Cryosurgery and electrosurgery came into use. Soon after the development of the laser in the 1950s, dermatologists used it to treat skin conditions. The surge of innovations has continued, making dermatology an exciting and rapidly evolving specialty.

How It Works

Skin diseases and conditions affect patients of all ages and ethnicities. Physicians may specialize in a specific age group, such as children, or a category of conditions. Some dermatologists focus on cosmetic disorders of the skin and may be certified to perform procedures such as injections of botulinum toxin, chemical peels, and laser therapy. Others concentrate on skin cancers or immunological conditions. Regardless of the focus of a dermatologist's practice, the day-to-day work can be divided into three main areas: diagnosis, treatment, and management.

Diagnosis. Dermatologists obtain the patient's medical history and assess their status. They examine the affected skin and adjacent areas to determine the nature and extent of the lesions. A frequently used method is dermoscopy (or epiluminescent microscopy), which employs a quality magnifying lens and a powerful lighting system to allow a close examination of the skin's structure. It is useful in evaluating pigmented skin lesions and can facilitate the diagnosis of melanoma.

Some skin conditions are more readily diagnosable than others. Acne and psoriasis, for example, often do not necessitate further tests. The lesions, however, may be of an ambiguous nature or potentially malignant. In these cases, the physician takes a tissue sample (for example, a biopsy or nail clippings) and submits it, usually with a differential diagnosis, to a laboratory. There, the sample undergoes a dermatopathological evaluation.

Dermatopathologists interpret tissue samples on specially prepared slides using light, fluorescent, and sometimes electron microscopy. They first determine how the specimen was obtained (for example, a punch or shave biopsy), then establish if the condition appears infectious, inflammatory, degenerative, or neoplastic (benign or malignant). Often, consultation with other dermatopathologists and the attending dermatologist or primary care physician is necessary. Additional sections of the specimen may be required before a diagnosis can be rendered and the report sent to the clinician. The work needs to be extremely thorough; no part of the microscopy slide can be left unexamined. Ancillary methods used by dermatopathologists include immunohistochemistry and flow cytometry.

Additional tests that may be undertaken in the dermatologist's office include a potassium hydroxide examination for fungi, bacterial stains, fungal and bacterial cultures, skin scrapings for scabies, patch tests (for contact allergies), and blood tests.

Treatment. Once the diagnosis has been made, treatment options are considered and discussed with the patient or caregiver. Dermatopathologists often play an active role in this process. Treatment may involve medications to be administered externally or internally, injections, or surgical procedures. Punch biopsy, shave biopsy, electrodesiccation and curettage, blunt dissection, and simple excision and suture closure are the basic techniques that dermatologists master. They are also familiar with more sophisticated techniques, such as Mohs micrographic surgery, and, if appropriate, may refer patients to physicians who perform these techniques.

Management. Skin conditions can be lifelong problems. Eczema, acne, and psoriasis are only a few of many conditions that require regular visits to the dermatologist. Managing the patient's condition often takes the form of control rather than cure.

Applications and Products

Dermatologists diagnose and treat many disorders and diseases. The most common examples of disorders treated are infections, inflammatory diseases, papulosquamous diseases, and tumors.

Infections. Several categories of pathogens cause infections with cutaneous manifestations. Staphylococcus aureus and group A beta-hemolytic streptococci account for most skin and soft tissue infections, such as impetigo, folliculitis, cellulitis, and furuncles. Syphilis is an infectious disease caused by the bacterium Treponema pallidum. Primary syphilis, acquired by direct contact with a skin or mucosal lesion, manifests with a cutaneous ulcer (chancre). Warts are benign epidermal tumors caused by numerous types of human papillomaviruses (HPVs). These viruses infect epithelial cells of the skin, mouth, and other areas, causing both benign and malignant lesions.

Herpesvirus infections are caused by herpes simplex virus 1 (HSV1) and herpes simplex virus 2 (HSV2), distinguishable by laboratory tests. HSV1 is generally associated with oral infections, and HSV2 causes genital infections. The lesions appear as grouped vesicles on a red base.

Dermatophytes (responsible for tinea or ringworm) and Candida species yeasts are agents that induce superficial fungal infections.

Inflammatory Diseases.Eczema is the most common inflammatory disorder. It manifests with itchiness and exhibits three clinical stages: acute (redness and vesicles), subacute (redness, scaling, fissuring, and scalded appearance), and chronic (thickened skin). There are numerous types of eczemas, including atopic dermatitis (in patients with personal or family history of allergies) and contact dermatitis (allergy to a common material such as nickel or poison oak).

Acne is a common disorder with critical psychosocial effects. It occurs in predisposed individuals when sebum production increases. The proliferation of the microorganism Propionibacterium acnes in the sebum alters it and causes pore clogging. Lesions are noninflammatory (comedones, also known as blackheads and whiteheads) or inflammatory (papules, pustules, or nodules). The extent and severity of the lesions varies from a few comedones to the strongly inflammatory acne conglobata.

Papulosquamous Diseases. The group of disorders known as papulosquamous diseases are characterized by scaly papules and plaques. Psoriasis, an immune-mediated skin and joint inflammatory disease, develops when inflammation primes basal stem keratinocytes to proliferate excessively. Initial red, scaling papules coalesce to form round-oval plaques. The scales are adherent, silvery-white, and show bleeding points when removed (Auspitz sign). Inflammatory arthritis is present in some patients.

Tumors. The two most common skin cancers are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Approximately 80 percent of nonmelanoma skin cancers are the basal cell type, and 20 percent are the squamous cell type.

Basal cell cancer, the most common invasive malignant skin tumor in humans, represents more than 90 percent of skin cancers in the United States. The patient typically has a bleeding or scabbing sore that heals and subsequently recurs. The tumor advances by direct extension and destroys normal tissue but rarely metastasizes. The cells of basal cell carcinoma resemble those of the basal epidermal layer. They have a large nucleus and develop an orderly line around the periphery of tumor nests (palisading).

Squamous cell carcinoma is the second most common cancer among light-skinned individuals. The relationship to ultraviolet radiation is stronger and the chances of metastasis much higher than for basal cell carcinoma. Actinic keratosis, the most common precursor of squamous cell carcinoma, begins on sun-exposed skin as isolated or multiple flat, pink-brown, rough lesions. Abnormal squamous cells originate in the epidermis from keratinocytes and proliferate indefinitely.

Malignant melanoma originates from melanocytes. Skin melanoma either begins on its own or develops from a preexisting lesion, such as a mole (nevus). One of the most aggressive tumors, melanoma can metastasize to any organ, including the brain and heart. Individuals who sunburn easily or who have experienced multiple or severe sunburns have a twofold to threefold increased risk of developing skin melanoma. The goal of specialists and patients alike is to recognize melanomas as early as possible in their development. Compared with common acquired melanocytic nevi, malignant melanoma tends to have four characteristics: asymmetry, border irregularity, color variation, and diameter enlargement (ABCD). These four characteristics are the primary criteria for clinical melanoma recognition. Changes in the shape and color of a mole are critical early signs and should always arouse suspicion. Ulceration and bleeding are late signs; at this stage, the chance of a cure diminishes greatly.

Important Treatment Modalities. Common ways of dealing with dermatological problems are topical treatments (such as ointments and creams) and oral treatments (drugs taken by mouth). Any bodily injury, irritation, or trauma that eliminates water, lipids, or protein from the epidermis compromises its function. Restoration of the normal epidermal barrier can often be accomplished using mild soaps and emollient creams or lotions. The often-cited dermatologic adage is “If it is dry, wet it; if it is wet, dry it.” Consequently, wet compresses are a frequently used remedy. A multitude of other topical treatments are available, from antibiotic, antiviral, or steroid ointments applied to treat infectious diseases or eczema to vitamin D derivative creams for psoriasis and retinoid creams for acne. Drugs can also be taken orally to treat a variety of conditions, such as acne and autoimmune disorders.

Surgical and Cosmetic Procedures. Dermatologists use several techniques to obtain skin biopsies. Most procedures are done in the doctor's office, and each technique has specific indications. Punch biopsies are employed for most superficial inflammatory diseases and skin tumors (except melanoma). Shave biopsies are used for superficial benign and malignant tumors. Deep inflammatory diseases and malignant melanoma benefit from excisions.

Electrodesiccation and curettage (ED&C; also known as scrape and burn) is an important technique for removing a variety of superficial skin lesions, such as cancerous growths and genital warts. The physician uses a sharp dermal curette to cut away the growth and a needle-shaped electrode that delivers an electric current to remove any remaining material and to stop the bleeding.

Blunt dissection is a fast, elementary, usually nonscarring surgical procedure used to remove warts and other epidermal tumors. Unlike ED&C and excision, it does not disturb normal tissue.

Small, superficial, nonmalignant lesions may be quickly and efficiently frozen with liquid nitrogen administered with a spray or sterile contact probe. Cryosurgery for malignant lesions, however, requires experience and sophisticated equipment with thermocouples that measure the depth of freeze. This minimally invasive technique is also successfully employed for common lesions, including genital warts, actinic keratoses, and certain infectious conditions.

An important surgical breakthrough occurred in the 1930s when physician Frederic Mohs developed a microscope-guided method of tracing and removing basal cell carcinomas. These—and other tumors—may not grow in a well-circumscribed fashion but instead extend in fingerlike projections. Thin layers of tissue are removed, and all margins of the specimen are mapped to determine whether any tumor remains. This tissue-sparing technique has high cure rates.

Chemical peeling of facial skin uses a caustic agent to achieve a controlled chemical burn of the epidermis and the outer dermis. Skin regeneration results in a fresh and orderly epidermis with ablation of fine wrinkles and pigmentation reduction.

In liposuction surgery, fat is removed through half-inch incisions using small-diameter cannulae. Multiple to-and-fro movements mechanically disrupt the fat and create tunnels. The loosened fat is removed by strong suction.

Photothermolysis is based on the property of a chromophore (melanin, hemoglobin, tattoo ink) in a target tissue to strongly absorb a selected laser wavelength and generate heat. It removes the target tissue while producing only a local thermal injury, resulting in less injury to the surrounding tissue and lowered risk of scarring. Vascular lesions, for example, can be treated in this manner, including port-wine stains, benign tumors, and spider veins in legs. In vascular lesions, the targeted chromophore is hemoglobin.

Specific types of lasers can be used to treat benign pigmented lesions with a predominant epidermal component such as freckles and tattoos. In addition, numerous laser-based devices can remove unwanted hair.

Other common techniques and devices include using intense pulsed light for resurfacing (to treat vascular lesions and acne) and light-activated drugs in photodynamic therapy (for precancerous and cancerous cells, acne, rosacea, or skin enhancement).

One of the most popular nonsurgical cosmetic procedures is injections of botulinum toxin (Botox). This neurotoxin blocks the release of the chemical messenger acetylcholine, effectively causing chemical denervation. The injections reduce facial lines caused by hyperfunctional muscles.

Careers and Course Work

Those considering a career in dermatology will require a strong foundation in biology, chemistry, and physics, followed by a decade of training and a lifetime of learning. Medical school requires four years of intense preparation in an accredited school. Subsequent specialization in dermatology requires a one-year internship, followed by a three-year residency in an accredited program. A one- or two-year fellowship can be undertaken after residency; examples of possible paths are dermatopathology, pediatric dermatology, immunodermatology, and dermatologic surgery. Veterinary colleges may also offer a three-year residency program in dermatology.

To pursue a career in dermatopathology, a physician can also specialize in surgical pathology via a three-year residency and then undergo further training in a dermatopathology fellowship program. Competency in dermatopathology is of utmost importance for both pathology and dermatology residents.

Opportunities to practice exist all over the United States and worldwide. Dermatopathologists and dermatologists can be self-employed, partner with others, or be employed by hospitals, clinics, and governmental agencies. Both categories of specialists teach in universities and colleges that have degree programs in these disciplines. Research opportunities are available in universities and laboratories operated by corporations, pharmaceutical companies, or governmental agencies.

Social Context and Future Prospects

The burden of skin diseases on society is significant. According to the American Academy of Dermatology, the annual cost of treating nonmelanoma skin cancer in the United States is about $4.8 billion, while the average annual cost of treating melanoma is about $3.3 billion. At any given time, one in three people in the United States suffers from an active cutaneous condition. The most prevalent disorders are herpes simplex, shingles, sun damage, eczema, warts, and hair and nail conditions. The incidence of melanoma is on the rise. Between 2013 and 2023, the number of new invasive melanoma cases increased each year by 27 percent, according to the Melonoma Research Alliance. The main reasons for this high level of skin disease are increased exposure to the sun during recreational activities and the atmospheric changes brought on by pollutants that result in increased radiation. Understanding the biology of skin tumors, especially melanoma, has become a priority of research efforts worldwide.

New therapeutic agents such as antibodies and immunomodulators offer hope for stubborn medical conditions such as psoriasis, still an incurable disease in need of promising long-term therapeutic approaches. Biological treatments are on their way to bringing relief. Stem cells hold promise for tissue regeneration.

Advances in understanding the pathogenesis of various disorders have led to improved management and to a reduced risk of incorporating nonevidence-based components into dermatological practice. The close cooperation between dermatologists, pathologists, rheumatologists, and surgeons enhances the quality and efficiency of care.

The ever-increasing preoccupation with young, healthy skin—especially due to the rise of social media—has fueled an unprecedented explosion in the popularity of cosmetic procedures. Dermatological fillers, laser and light therapies, chemical peels, plasma therapies, body contouring, and stem cell therapies are now commonplace in dermatology. More critically, skin diseases with significant aesthetic, psychological, and social consequences have prompted dermatologists to implement and refine numerous cosmetic techniques involving peeling, botulinum toxin, hyaluronic acid, and lasers. These techniques have enabled many categories of patients with skin disorders to lead an active social life.

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